Search

In recent times, it has been perceived that incorporation of branes in higher dimensional theories of quantum gravity is very effective to differentiate those theories which successfully satisfy the swampland criteria. Moreover, warm inflation is considered to be most appropriate single scalar field inflationary model in the framework of swampland criteria. In this regard, we study two well-known Chaplygin gas (CG) models embedded in Randall–Sundrum braneworld. It is known that the de Sitter constraint is derived by taking into account Bousso's covariant entropy bound. We discuss the application of this result in the context of Chaplygin-brane models and find the condition on the slope of the potential. Furthermore, it is demonstrated that in view of warm inflation dynamics this condition remains essentially unchanged indicating the compatibility of the models with swampland criteria. In addition, we investigate the constraint on the warm inflation parameter imposed by the de Sitter conjecture which shows that the warm inflation is in accordance with de Sitter bound in the strong as well as in weak dissipative regime for both models of Chaplygin gas. [ABSTRACT FROM AUTHOR]

Partially massless theory in three dimensions is revisited and its relationship with the self-dual massive gravity is considered. The only mode of the partially massless theory is shown explicitly through an action for a scalar field on (A)dS background. This fact can be generalized to higher dimensions. This degree of freedom is altered when a triadic Chern-Simons is introduced, giving rise to the self-dual massive gravity on (A)dS background. We present another physical system with partially massless symmetry and its connection with topologically massive gravity is discussed. [ABSTRACT FROM AUTHOR]

We discuss the implications of a purely classical (instead of quantum) theory of gravity for the primordial gravitational wave spectrum generated during inflation. We argue that for a scalar field driven inflation in a classical gravity the amplitude of the gravitational wave will be too small, irrespective of its primordial seed, to be detected in any forthcoming experiments. Therefore, a positive detection of the B-mode polarizations in the Cosmic Microwave Background (CMB) spectrum will naturally confirm the quantum nature of gravity itself. Furthermore there will be no upper limit on the scale of inflation in the case of classical gravity, and a high-scale model of inflation can easily bypass the observational constraints. [ABSTRACT FROM AUTHOR]

We review on a recent construction of the on-shell supersymmetric brane action for the codimension-two branes with nonzero tension in the flux compactification of a 6D chiral gauged supergravity. On dimensionally reducing on 4D gauged supergravity for a new supersymmetric unwarped background with conical branes, we consider the modulus stabilization for determining the soft masses of the scalars localized on the branes and show that the bulk U(1)R provides a new mechanism for mediating the SUSY breaking. [ABSTRACT FROM AUTHOR]

We investigate coupled gravity and a bulk scalar field on a slice of AdS5 bulk with special BPS branes at the two ends. With a careful treatment of the general coordinate invariance, the complete tensor–scalar spectrum is presented. There are two massless zero modes in the scalar sector, the radion and a dilatonic zero mode. The four-dimensional effective action is of biscalar–tensor type. [ABSTRACT FROM AUTHOR]

Recently Gambini and Pullin proposed a new consistent discrete approach to quantum gravity and applied it to cosmological models. One remarkable result of this approach is that the cosmological singularity can be avoided in a general fashion. However, whether the continuum limit of such discretized theories exists is model dependent. In the case of massless scalar field coupled to gravity with Λ=0, the continuum limit can only be achieved by fine tuning the recurrence constant. We regard this failure as the implication that cosmological constant should vary with time. For this reason we replace the massless scalar field by Chaplygin gas which may contribute an effective cosmological constant term with the evolution of the universe. It turns out that the continuum limit can indeed be reached in this case. [ABSTRACT FROM AUTHOR]

We analyze the relationship between classical chaos and particle creation in Robertson–Walker cosmological models with gravity coupled with a scalar field. Within our class of models chaos and particle production are seen to arise in the same cases. Particle production is viewed as the seed of decoherence, which enables the quantum to classical transition and ensures that the correspondence between the quantum and classically chaotic models will be valid. [ABSTRACT FROM AUTHOR]